Conductive thin film for semiconductor device, semiconductor device, and method of manufacturing the same

ABSTRACT

A semiconductor device  1  obtained by depositing, on a substrate  2 , a gate electrode  4  formed by a conductive thin film containing Mo atoms and Ag atoms, a gate insulating film  6 , an α-Si:H(i) film  8 , a channel protection layer  10 , an α-Si:H(n) film  12 , a source/drain electrode  14  formed by a conductive thin film containing Mo atoms and Ag atoms, a source/drain insulating film  16 , and a drive electrode  18 . By using a conductive thin film containing Mo atoms and Ag atoms, the gate electrode  4  and the source/drain electrode  14  are formed to manufacture the semiconductor device  1 . Thus, the conductive thin film for a semiconductor device, having high adhesion strength to a substrate, an insulating layer, and the like, a semiconductor device which operates stably without deteriorating the performance, and a method of efficiently manufacturing the conductive thin film and the semiconductor device can be provided.

TECHNICAL FIELD

[0001] The present invention relates to a conductive thin film for asemiconductor device such as a semiconductor transistor, a semiconductordevice, and a method of manufacturing the same.

BACKGROUND ART

[0002] A TFT is a very important component as a main component of adisplay of a portable personal computer, a laptop personal computer, atelevision, or the like.

[0003] Companies manufacture TFTs by their methods. Since the process ofmanufacturing a TFT is complicated and various metals and metal oxidesare deposited a plurality of times, simplification of the process isdemanded.

[0004] In a process of manufacturing a conventional TFT array, asmaterials of a gate electrode and a source/drain electrode, metals suchas Cr and TaW are used.

[0005] Although Cr is easily processed, there is a problem that Cr iseasily corroded. Although TaW is resistive to corrosion and the like, ithas a problem of high electric resistance and the like.

[0006] Consequently, a TFT array using wires made mainly of aluminum asa metal which is easily processed and has low electric resistance hasbeen proposed.

[0007] However, when an aluminum electrode is in direct contact with asilicon layer and a drive electrode, problems occur such that aluminumis diffused into the silicon layer, thereby deteriorating deviceperformance, and aluminum is oxidized and converted into alumina, itincreases the electric resistance with the drive electrode, and thedevice does not operate normally.

[0008] Attempt is being made to reduce the contact resistance with thedrive electrode by sandwiching the aluminum electrode by Mo or Ti.

[0009] In order to sandwich the aluminum electrode, however, a film madeof Mo or Ti has to be formed first, after that, a film of a metalcontaining aluminum as a main component is formed, and a film made of Moor Ti has to be formed again. Consequently, there is a drawback that theprocess is complicated.

[0010] On the other hand, attempt is also being made to solve theproblem by using a silver or copper electrode. However, silver andcopper have low adhesion to with a silicon nitride film, a siliconwafer, or the like which is made of glass or an insulating film. Itcauses a problem such that silver and copper come off during themanufacturing process.

[0011] An object of the invention is to provide a conductive thin filmfor a semiconductor device having strong adhesion to a substrate, aninsulating layer, or the like, a semiconductor device that stablyoperates without deteriorating performance, and a method of efficientlymanufacturing the film and the device.

[0012] The inventors herein have studied wholeheartedly and, as aresult, found that the object can be achieved by using a conductive thinfilm containing Ag atoms and Mo atoms for a gate electrode and/or asource/drain electrode of a semiconductor device.

DISCLOSURE OF INVENTION

[0013] According to the present invention, a conductive thin filmcontaining Ag atoms and Mo atoms, having strong adhesion to a substrate,an insulating layer, and the like, and particularly preferably used fora semiconductor device is provided.

[0014] A semiconductor device in which at least one of a gate electrodeand a source/drain electrode is made by the conductive thin film isprovided.

[0015] By forming a gate electrode and/or a source/drain electrode fromthe conductive thin film, even when an electrode wire is in directcontact with a silicon layer, diffusion of metal atoms into the siliconlayer can be prevented, so that the performance of a semiconductordevice obtained does not deteriorate.

[0016] Further, even when a drive electrode is formed directly on theelectrode wire, contact resistance can be prevented from beingincreased. Thus, a semiconductor device which operates stably can beobtained.

[0017] Particularly, an example of the semiconductor device is asemiconductor transistor including a field effect transistor such as aTFT. In an example of a concrete structure, a gate electrode, asemiconductor layer, a source/drain electrode, and a drive electrode aredisposed on a substrate.

[0018] In a conductive thin film for a semiconductor device (conductivethin film) according to the invention, preferably, the film contains 0.5to 70% by weight of Mo atoms.

[0019] Further, more preferably, the conductive thin film of theinvention contains 30 to 99.5% by weight of Ag atoms and 0.5 to 70% byweight of Mo atoms. Further more preferably, the conductive thin filmcontains 70 to 99% by weight of Ag atoms and 1 to 30% by weight of Moatoms. Further more preferably, the conductive thin film contains 85 to98% by weight of Ag atoms and 2 to 15% by weight of Mo atoms.

[0020] By setting the Ag atoms and Mo atoms within the ranges, theadhesion between the conductive thin film and a substrate or aninsulating layer can be largely increased. Consequently, the conductivethin film can be preferably applied to a semiconductor device.

[0021] In the case of using the conductive thin film of the inventionfor a semiconductor device, at least one of the gate electrode and thesource/drain electrode is formed by the conductive thin film containingAg atoms and Mo atoms at any of the rates.

[0022] In the conductive thin film of the invention, preferably,resistivity is 5 μΩ·cm or less.

[0023] Further, in a semiconductor device of the invention, preferably,at least one of the gate electrode and the source/drain electrode isformed by the conductive thin film containing Ag atoms and Mo atoms andhaving resistivity of 5 μΩ·cm or less.

[0024] By setting the resistivity to be within the range, delay of asignal for driving a liquid crystal or the like can be effectivelyprevented.

[0025] In the conductive thin film of the invention, preferably, the Moatoms are Mo atoms derived from an Mo/Al compound, an Mo/Be compound, anMo/Ga compound, an Mo/Ge compound, an Mo/Ir compound, an Mo/Pt compound,an Mo/Re compound, an Mo/Si compound, an MoW alloy, an MoTa alloy, or anMoRh alloy.

[0026] When the Mo atoms are derived from any of such materials,dispersibility of the Mo atoms is improved and stability of theconductive thin film can be improved.

[0027] Another aspect of the present invention relates to a method ofmanufacturing a conductive thin film, wherein the conductive thin filmis formed by sputtering. In the method, it is preferable to use asputtering target containing Ag atoms and Mo atoms. Further anotheraspect of the invention relates to a method of manufacturing asemiconductor device, for forming at least one of a gate electrode and asource/drain electrode by a conductive thin film formed by using themethod of manufacturing the conductive thin film.

[0028] By forming a film by sputtering, a process of depositingMo/Al/Mo, Ti/Al/Ti or the like can be simplified and a semiconductordevice can be manufactured efficiently.

[0029] By using a sputtering target mainly made of Ag to which an Mocompound such as an Mo/Al compound, an Mo/Be compound, an Mo/Gacompound, an Mo/Ge compound, an Mo/Ir compound, an Mo/Pt compound, anMo/Re compound, an Mo/Si compound, an MoW alloy, an MoTa alloy, or anMoRh alloy is added, dispersibility of Mo is improved and a film can bestably formed by sputtering.

[0030] According to the method, adhesiveness of the gate electrode andthe source/drain electrode to a substrate (for example, glass substrate)and a silicon layer (such as silicon nitride film, semiconductor layer,or silicon wafer) is high and peeling does not occur during amanufacturing process. Thus, a semiconductor can be manufactured stably.

[0031] Further, it is preferable to use a sputtering target obtained byreducing, rolling, and sintering a mixture made of one or more kinds ofoxides selected from oxides of Al, Be, Ga, In, Ge, Ir, Pt, Re, Si, W,Ta, and Rh, an Ag oxide, and an Mo oxide.

[0032] By using such a sputtering target, a film can be formed stably atthe time of sputtering.

BRIEF DESCRIPTION OF DRAWING

[0033]FIG. 1 is a cross sectional view showing an embodiment of asemiconductor device of the present invention.

BEST MODE FOR CARRYING OUT THE INVENTION

[0034] A conductive thin film, a semiconductor device, and a method ofmanufacturing the same will be described hereinbelow.

1. Conductive Thin Film

[0035] (1) Kinds

[0036] A conductive thin film of the invention contains Ag atoms and Moatoms. For example, a single Ag as an Ag atom source is used as a maincomponent and an Mo atom is added to the Ag atom.

[0037] A Mo atom source is not particularly limited. Mo atoms may beadded as single Mo atoms or as a alloy compounds a metal mixture, or ametal compound.

[0038] Examples are Mo/Al compounds, Mo/Be compounds, Mo/Ga compounds,Mo/Ge compounds, Mo/Ir compounds, Mo/Pt compounds, Mo/Re compounds,Mo/Si compounds, MoW alloys, MoTa alloys, MoRe alloys, and the like.

[0039] Examples of the Mo/Al compounds are MoAl₁₂, MoAl₅, Mo₃Al₈, andMo₃Al. Examples of the Mo/Be compounds are MoBe₁₂, MoBe₂₂, Mo₃Be, andMoBe₂. Examples of the Mo/Ga compounds are Mo₃Ga and Mo₆Ga₃₁. Examplesof Mo/Ge compounds are MoGe₂, Mo₂Ge₃, Mo₃Ge, and Mo₃Ge₂. Examples of theMo/Ir compounds are MoIr and MoIr₃. An example of Mo/Pt compound isMoPt₃. An example of the Mo/Re compound is MoRe. Examples of the Mo/Sicompounds are MoSi₂, Mo₃Si, and Mo₅Si₃.

[0040] As a third component, another metal atoms may be added togetherwith the Mo atoms to the Ag atoms.

[0041] The kind of the third component is not particularly limited aslong as it is a metal which is not diffused into the silicon layer or ametal which does not exert an influence on the performance of asemiconductor device when it is diffused. Examples of such a componentare Pd, W, Cu, and Au.

[0042] The addition amount of the third component is not particularlylimited as long as it is in a range where no influence is exerted on theconductivity of the conductive thin film and the performance of thesemiconductor device.

[0043] (2) Ratio

[0044] In the case of using the conductive thin film for an electrode,preferably, 0.5 to 70% by weight of Mo atoms is contained for thefollowing reasons. When the content of Mo becomes lower than 0.5% byweight, an effect of adding Mo may not be displayed. On the other hand,when the content of Mo exceeds 70% by weight, there is a case that theresistance value of the gate electrode and that of the source/drainelectrode increase or there is a case that abnormal discharge duringsputtering increases.

[0045] For such reasons, it is most preferable to set the content of Moatoms in a conductive thin film to 2 to 15% by weight.

[0046] (3) Resistivity

[0047] The resistivity of the conductive thin film is preferably 5 μΩ·cmor less. The reason is that when the resistivity exceeds 5 μΩ·cm, delayin a signal for driving a liquid-crystal or the like may occur.

[0048] For such a reason, it is more preferable to set the resistivityof the conductive thin film to 3 μΩ·cm less.

2. Method of Manufacturing Conductive Thin Film

[0049] A conductive thin film of the invention is formed by sputtering.

[0050] In this case, a sputtering method and a sputtering system are notparticularly limited. Examples of the sputtering method arehigh-frequency sputtering, DC sputtering, RF sputtering, DC magnetronsputtering, RF magnetron sputtering, ECR plasma sputtering, and ion beamsputtering.

[0051] A sputtering target is not particularly limited as long as it isa target for forming a conductive thin film satisfying a targetperformance. Sputtering targets suitably used are, for example, asputtering target obtained by reducing, rolling, and sintering a mixtureof an Ag oxide and an Mo oxide, a sputtering target obtained byreducing, rolling, and sintering a mixture of one or more kinds ofoxides selected from the group of Al, Be, Ga, In, Ge, Ir, Pt, Re, Si, W,Ta, and Rh, Ag oxide, and Mo oxide, a sputtering target obtained byinserting a plate made of Mo singly or an Mo alloy into an Ag target apart of which is cut and removed, and a sputtering target obtained byinserting a plate made of Ag singly into a target of single Mo or an Moalloy a part of which is cut and removed. By using such a sputteringtarget, a film can be stably formed at the time of sputtering.

3. Semiconductor Device

[0052] The semiconductor device of the invention has a gate electrodeand a source/drain electrode formed by the conductive thin film. Theconstitution (substrate, silicon layer, drive electrode, and the like)other than the gate electrode and/or the source/drain electrode is notparticularly limited but can be made of normal materials.

[0053] In the invention, at least one of the gate electrode and thesource/drain electrode may be formed by the conductive thin film. Inthis case, as a material of an electrode which is not formed by theconductive thin film, a normal material can be used. Further, in thecase where wiring is necessary, from the viewpoint of the constitutionof the semiconductor device, a conductive thin film may be used aswiring.

4. Method of Manufacturing Semiconductor Device

[0054] In the method of manufacturing the semiconductor device of theinvention, at least one of the gate electrode and the source/drainelectrode is formed from the conductive thin film formed by using themethod of manufacturing the conductive thin film.

[0055] In this case, means for patterning the conductive thin filmformed by sputtering into a target electrode shape is not particularlylimited but may be performed by using photoetching or the like.

[0056] Further, in the semiconductor device of the invention, the methodof manufacturing components other than the electrodes is not limited butmay be a normal method using a normal material.

EXAMPLES

[0057] The invention will be described in more detail hereinbelow on thebasis of examples. However, the invention is not limited to theexamples.

Example 1

[0058] A sputtering target obtained by opening a hole of 10 mmφ in an Agtarget of 1.4 inches φ and inserting an Mo target of 10 mmφ into thehole was used and a thin film having a film thickness of 2,000 Å wasformed on a silicon wafer by DC magnetron sputtering at a substratetemperature of 300° C. The content of Mo in the thin film was 5.1% byweight and resistivity was 2.4 μΩ·cm. Adhesion strength by a scratchtest of the thin film was 5.57N. The scratch test was conducted asfollows.

[0059] (1) Measurement Principle

[0060] A coated substrate is scratched with a diamond cone at constantspeed while increasing a load at constant speed, and a destruction whichoccurs in or on the thin film is detected by an AE sensor. By using aload at which an AE signal rapidly goes high as a critical load, aquantitative value of adhesion strength is obtained.

[0061] By observing the surface after the scratch, a load of destruction(interface peel, film base material destruction, and the like) in apredetermined aspect is calculated.

[0062] In measurement of this time, as a result of surface observationafter scratch, the substrate was exposed at the critical load value orless. Consequently, adhesion strength was calculated by the lattermethod.

[0063] (2) Apparatus and Measurement Conditions

[0064] scratch tester: Micro-Scratch-Tester manufactured by CSEM

[0065] scratch distance: 10.0 mm

[0066] scratch load: 0 to 10.0N

[0067] load rate: 10.0 N/min

[0068] scratch speed 10.0 mm/min

[0069] diamond cone shape: tip R: 200 μm (120°)

[0070] (3) Calculation of Adhesion Strength

[0071] A sample of each scratch test was observed by a light microscope.A point where a silicon wafer as a substrate is exposed was used as apeel point of the film and the distance from the scratch start point wasmeasured, thereby calculating a peel load. The results are shown inTable 1.

[0072] Examples 2 to 4

[0073] Thin films were formed in a manner similar to Example 1 exceptthat the content of Mo and the content of the third metal in thesputtering target were changed as shown in Table 1, and evaluation wasmade. The results are shown in Table 1.

[0074] Comparative Example 1

[0075] A thin film was formed in a manner similar to Example 1 exceptthat the Mo target was not used but only the Ag target was used, andevaluation was made. The result is shown in Table 1. TABLE 1 The thirdAdhesion Mo content metal content Resistivity strength (wt %) (wt %) (μΩ· cm) (N) Example 1 5.1 — 2.4 5.57 Example 2 2.1 0.5 (Cu) 2.3 5.71Example 3 2.6 1.0 (In) 2.7 5.84 Example 4 2.5 0.6 (Ga) 3.8 5.12Comparative 0 — 2.1 0.40 example 1

Example 5

[0076] An embodiment of the invention will be described by using FIG. 1.

[0077]FIG. 1 is a cross sectional view showing an embodiment of asemiconductor device of the invention.

[0078] On a light transmittable glass substrate 2, a metal Ag(resistivity: 2.4 μΩ·cm) containing 5% by weight of Mo was deposited toa film thickness of 2,500 Å by high frequency sputtering. The layer wassubjected to photoetching using a nitric acid-acetic acid-phosphoricacid solution as an etchant, thereby forming a gate electrode 4 (gateelectrode wire) of a desired shape.

[0079] Next, a gate insulating film 6 as a first silicon nitride (SiNx)film (silicon layer) was deposited to a film thickness of 3,000 Å.

[0080] Subsequently, a SiH₄—N₂ mixed gas was used as a discharge gas andan α-Si:H(i) film (silicon layer) 8 was deposited to a film thickness of3,500 Å.

[0081] Further, on the α-Si:H(i) film 8, by using an SiH₄—NH₃—N₂ mixedgas as a discharge gas, a second silicon nitride (SiNx) film wasdeposited to a film thickness of 3,500 Å. From the second SiNx film, adesired channel protective layer (silicon layer) 10 was formed by dryetching using a CF₄ gas.

[0082] Subsequently, an α-Si:H(n) film (silicon layer) 12 was depositedto a film thickness of 3,000 Å by using an SiH₄—H₂—PH₃ mixed gas.

[0083] The gate insulating film 6, α-Si:H(i) film (silicon layer) 8,channel protection layer (silicon layer) 10, and α-Si:H(n) film (siliconlayer) 12 were deposited by glow discharge CVD.

[0084] After that, Ag (resistivity: 3.6 μΩ·cm) containing 2% by weightof MoPt₃ was deposited to a film thickness of 0.3 μm by sputtering. Thislayer was subjected to photoetching using a nitric acid-aceticacid-phosphoric acid solution as an etchant, thereby patterning adesired source/drain electrode 14.

[0085] Further, by performing both dry etching using a CF₄ gas and wetetching using a hydrazine (NH₂NH₂.H₂O) solution on the α-Si:H film, thepattern of the α-Si:H(i) film 8 and the pattern of the α-Si:H(n) film 12were formed as desired patterns.

[0086] On the desired patterns, a source/drain insulating film (siliconlayer) 16 as a third silicon nitride (SiNx) film was deposited to a filmthickness of 3,000 Å by glow discharge CVD. At this time, a SiH₄—NH₃—N₂mixed gas was used as a discharge gas to form the third SiNx film.

[0087] Further, by photoetching using the dry etching with the CF₄ gas,a desired through hole was formed as an output port of the gateelectrode 4, an output port of the source electrode 14, and an electriccontact point between the drain electrode 14 and a pixel electrode(drive electrode) 18.

[0088] After that, by making argon plasma act on the surface of themetal Ag electrode, the surface was cleaned. An amorphous transparentconductive film made of indium oxide and zinc oxide as main componentswas deposited by sputtering. As a target, an In₂O₃—ZnO sintered body inwhich the atom ratio [In/(In+Zn)] between In and Zn was adjusted to 0.83and which is disposed in a planar magnetron cathode was used. By using,as a discharge gas, an argon gas obtained by mixing pure argon or anoxygen gas of a small amount of about 1% by volume, a transparentelectrode film was deposited to a film thickness of 1,200 Å.

[0089] When the In₂O₃—ZnO film was analyzed by the X-ray diffractionmethod, no peak was observed and the film was amorphous. The film waspatterned into the desired pixel electrode 18 and a lead electrode byphotoetching using a solution of 3.4% by weight of oxalic acid and,further, a light shielding film pattern was formed, thereby completingan α-SiTFT substrate.

[0090] A TFT-LCD flat-panel display was manufactured by using thesubstrate. After that, when a video signal was input and displayperformance was checked, the display performance was excellent.

Comparative Example 2

[0091] Comparative Example 2 was carried out in a manner similar toExample 5 except that metal Al (resistivity: 7 μΩ·cm) containing 2% byweight of Nd was used for the Ag/Mo and Ag/Mo/Pt wires in Example 5. Inthe display performances of the case, color developed spots weregenerated in the vertical and lateral directions and it was recognizedthat a signal was not input normally.

INDUSTRIAL APPLICABILITY

[0092] According to the invention, a conductive thin film for asemiconductor device having high adhesion strength to a base material,an insulating layer, and the like, the semiconductor device whichoperates stably without deteriorating performance, and the method ofefficiently manufacturing the same can be provided.

1. A conductive thin film for a semiconductor device, containing Agatoms and Mo atoms.
 2. The conductive thin film for a semiconductordevice according to claim 1, wherein the film contains 0.5 to 70% byweight of Mo atoms.
 3. The conductive thin film for a semiconductordevice according to claim 1, wherein resistivity is 5 μΩ·cm or less. 4.The conductive thin film for a semiconductor device according to claim1, wherein the Mo atoms are Mo atoms derived from an Mo/Al compound, anMo/Be compound, an Mo/Ga compound, an Mo/Ge compound, an Mo/Ir compound,an Mo/Pt compound, an Mo/Re compound, an Mo/Si compound, an MoW alloy,an MoTa alloy, or an MoRh alloy.
 5. A method of manufacturing theconductive thin film for a semiconductor device according to claim 1,wherein the conductive thin film is formed by sputtering.
 6. The methodof manufacturing the conductive thin film for a semiconductor deviceaccording to claim 5, wherein a sputtering target obtained by reducing,rolling, and sintering a mixture made of an Ag oxide and an Mo oxide isused.
 7. The method of manufacturing a conductive thin film for asemiconductor device according to claim 5, wherein a sputtering targetobtained by reducing, rolling, and sintering a mixture made of one ormore kinds of oxides selected from oxides of Al, Be, In, Ga, Ge, Ir, Pt,Re, Si, W, Ta, and Rh, an Ag oxide, and an Mo oxide is used.
 8. Asemiconductor device, wherein at least one of a gate electrode and asource/drain electrode is formed by the conductive thin film for asemiconductor device according to claim
 1. 9. A method of manufacturingthe semiconductor device according to claim 8, wherein at least one of agate electrode and a source/drain electrode is formed by a conductivethin film formed by using the method of manufacturing a conductive thinfilm for a semiconductor device according to claim 5.